Solution for Google Requirement to use GTIN for Variable Products
It's my understanding that Google Merchant will require GTIN for all products by 5/16/16. Stores selling Variable products with size/color variations will now need to create 20+ variations for each product and load the GTIN from there.
For anyone else reading this, the Google Product Feed official extension supported this prior to the deadline, and still does today.
It provides a field for storing GTINs (or any of the supported feed attributes) which can be set either at the main product, or against individual variations.
This will solve the Problem, but WOO Support want more Votes till they will do. :(